For the processing of sheet material, in particular bank notes, it is provided that the bank notes are input to an input area as loose stacks and singled by a singler. The individual bank notes are transferred by the singler to a transport system and supplied to processing. Conventional forms of processing for bank notes are acceptance, checking and recognition of the bank notes by means of sensors, whereby authenticity, type (currency, denomination), state (soiling, damage), etc., are ascertained. Based on the results of checking and recognition, the bank notes are thereafter e.g. sorted, stacked, bundled, destroyed, etc.
For the processing of bank notes in bank-note processing machines it is of fundamental importance that the bank notes are actually each present individually after singling by the singler. Hence, in the past a multiplicity of improvements have been proposed for improving the quality of singling and ensuring that only one bank note at a time is singled by the singler and in particular preventing the simultaneous singling of two or more bank notes.
For this purpose, elaborate mechanical improvements of the singler itself have for example been proposed. Likewise, it has been proposed to provide sensors immediately after the singler for ascertaining whether the singler has grasped more than one bank note upon singling.
Further problems occur upon singling when not only bank notes but also foreign bodies are input to the input area. These may be for example paper clips and staples that are fastened to one or more bank notes. However, the input bank notes frequently also include coins, credit cards or other objects that are usually kept together with bank notes. Such foreign bodies cause extreme disturbances in the singling of the bank notes. Normally it is necessary to employ a service person to remedy the resulting disturbances, because the foreign bodies block or damage the singler or even cause destruction of the singler or other parts of the bank-note processing machine, e.g. the transport system or the sensors of the bank-note processing machine.
Proposals have also been made in the past for remedying such problems. For example, sensors have been disposed in the input area for ascertaining the presence of metallic foreign bodies. This makes it possible to ascertain the presence of coins, paper clips, etc., and to terminate or even prevent the onset of the singling process, but non-metallic foreign bodies, e.g. credit cards, are not recognized and lead to the above-described problems.